<!DOCTYPE HTML>
<html>
<!--
https://bugzilla.mozilla.org/show_bug.cgi?id=1247074
-->
<head>
  <meta charset="utf-8">
  <title>Test for Bug 1247074</title>
  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
  <script type="text/javascript" src="/tests/SimpleTest/paint_listener.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
  <style>
  .outer {
      direction: ltr;
      height: 400px;
      width: 415px;
      overflow: hidden;
      position: relative;
  }
  .inner {
      height: 100%;
      outline: none;
      overflow-x: hidden;
      overflow-y: scroll;
      position: relative;
      scroll-behavior: smooth;
  }
  .outer.contentBefore::before {
      top: 0;
      content: '';
      display: block;
      height: 2px;
      position: absolute;
      width: 100%;
      z-index: 99;
  }
  </style>
</head>
<body>
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1247074">Mozilla Bug 1247074</a>
<p id="display"></p>
<div class="outer">
  <div class="inner">
   <ol>
    <li>Some text</li>
    <li>Some text</li>
    <li>Some text</li>
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    <li>Some text</li>
    <li>Some text</li>
    <li>Some text</li>
    <li>Some text</li>
    <li>Some text</li>
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    <li>Some text</li>
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    <li>Some text</li>
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    <li>Some text</li>
    <li>Some text</li>
   </ol>
  </div>
</div>
<script>
SimpleTest.waitForExplicitFinish();
window.onload = function() {
  var elm = document.getElementsByClassName('inner')[0];

  // Take control of the refresh driver
  var utils = SpecialPowers.DOMWindowUtils;
  utils.advanceTimeAndRefresh(0);

  // Start a smooth scroll and advance a couple of frames so we're in the
  // middle of the scroll animation
  elm.scrollTop = 500;
  utils.advanceTimeAndRefresh(16);
  utils.advanceTimeAndRefresh(16);

  // Trigger a frame reconstruction
  elm.parentNode.classList.add('contentBefore');

  // Reach a stable state and verify the scroll position is 500
  utils.restoreNormalRefresh();
  waitForAllPaintsFlushed(function() {
    SimpleTest.is(elm.scrollTop, 500, "Scroll position ended up at 500");
    SimpleTest.finish();
  });
}

</script>
</body>
</html>
